The paint layer of motorcars is generally composed of three layers, i.e. an undercoat layer, an intermediate coat layer and an overcoat layer. The overcoat layer is formed by coating a metallic base paint containing a metallic pigment on an intermediate coated plate and then coating a clear paint thereon without baking or curing the metallic base coating (i.e. by so-called "wet-on-wet" method), followed by baking or curing the metallic base coating and clear coating (i.e. by so-called "two coat one bake" method).
The metallic base paint used in this method can exhibit excellent surface appearance in case where flake-like metallic pigment, such as aluminum pigment, is uniformly orientated therein.
Japanese Kokai Publication 58-168664 discloses an aqueous paint which contains an aqueous polyurethane dispersant. However, a problem has occurred in surface appearance because the metallic pigment is not uniformly orientated.
Japanese Kokai Publication 1-287183 discloses an aqueous metallic base paint which contains an acrylic emulsion, a urethane emulsion and a cross-linking agent. Since the paint is an aqueous dispersion, environmental pollution problems do not come about in comparison with solvent type paint, but a problem often occurs in orientation of a metallic pigment and a surface appearance is not always satisfactory.